39 ideas
| 7689 | The modal logic of C.I.Lewis was only interpreted by Kripke and Hintikka in the 1960s [Jacquette] |
| Full Idea: The modal syntax and axiom systems of C.I.Lewis (1918) were formally interpreted by Kripke and Hintikka (c.1965) who, using Z-F set theory, worked out model set-theoretical semantics for modal logics and quantified modal logics. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: A historical note. The big question is always 'who cares?' - to which the answer seems to be 'lots of people', if they are interested in precision in discourse, in artificial intelligence, and maybe even in metaphysics. Possible worlds started here. |
| 7681 | Logic describes inferences between sentences expressing possible properties of objects [Jacquette] |
| Full Idea: It is fundamental that logic depends on logical possibilities, in which logically possible properties are predicated of logically possible objects. Logic describes inferential structures among sentences expressing the predication of properties to objects. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: If our imagination is the only tool we have for assessing possibilities, this leaves the domain of logic as being a bit subjective. There is an underlying Platonism to the idea, since inferences would exist even if nothing else did. |
| 7682 | Logic is not just about signs, because it relates to states of affairs, objects, properties and truth-values [Jacquette] |
| Full Idea: At one level logic can be regarded as a theory of signs and formal rules, but we cannot neglect the meaning of propositions as they relate to states of affairs, and hence to possible properties and objects... there must be the possibility of truth-values. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: Thus if you define logical connectives by truth tables, you need the concept of T and F. You could, though, regard those too as purely formal (like 1 and 0 in electronics). But how do you decide which propositions are 1, and which are 0? |
| 7697 | On Russell's analysis, the sentence "The winged horse has wings" comes out as false [Jacquette] |
| Full Idea: It is infamous that on Russell's analysis the sentences "The winged horse has wings" and "The winged horse is a horse" are false, because in the extant domain of actual existent entities there contingently exist no winged horses | |
| From: Dale Jacquette (Ontology [2002], Ch. 6) | |
| A reaction: This is the best objection I have heard to Russell's account of definite descriptions. The connected question is whether 'quantifies over' is really a commitment to existence. See Idea 6067. |
| 7701 | Can a Barber shave all and only those persons who do not shave themselves? [Jacquette] |
| Full Idea: The Barber Paradox refers to the non-existent property of being a barber who shaves all and only those persons who do not shave themselves. | |
| From: Dale Jacquette (Ontology [2002], Ch. 9) | |
| A reaction: [Russell spotted this paradox, and it led to his Theory of Types]. This paradox may throw light on the logic of indexicals. What does "you" mean when I say to myself "you idiot!"? If I can behave as two persons, so can the barber. |
| 7707 | To grasp being, we must say why something exists, and why there is one world [Jacquette] |
| Full Idea: We grasp the concept of being only when we have satisfactorily answered the question why there is something rather than nothing and why there is only one logically contingent actual world. | |
| From: Dale Jacquette (Ontology [2002], Conclusion) | |
| A reaction: See Ideas 7688 and 7692 for a glimpse of Jacquette's answer. Personally I don't yet have a full grasp of the concept of being, but I'm sure I'll get there if I only work a bit harder. |
| 7692 | Being is maximal consistency [Jacquette] |
| Full Idea: Being is maximal consistency. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: You'll have to read Ch.2 of Jacquette to see what this is all about, but as it stands it is a lovely slogan, and a wonderful googly/curve ball to propel at Parmenides or Heidegger. |
| 7687 | Existence is completeness and consistency [Jacquette] |
| Full Idea: A combinatorial ontology holds that existence is nothing more or less than completeness and consistency, or what is also called 'maximal consistency'. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: You'll have to read Jacquette to understand this one! The claim is that existence is to be defined in terms of logic (and whatever is required for logic). I take this to be a bit Platonist (rather than conventionalist) about logic. |
| 7679 | Ontology is the same as the conceptual foundations of logic [Jacquette] |
| Full Idea: The principles of pure philosophical ontology are indistinguishable ... from the conceptual foundations of logic. | |
| From: Dale Jacquette (Ontology [2002], Pref) | |
| A reaction: I would take Russell to be an originator of this view. If the young Wittgenstein showed that the foundations of logic are simply conventional (truth tables), this seems to make ontology conventional too, which sounds very odd indeed (to me). |
| 7678 | Ontology must include the minimum requirements for our semantics [Jacquette] |
| Full Idea: The entities included in a theoretical ontology are those minimally required for an adequate philosophical semantics. ...These are the objects that we say exist, to which we are ontologically committed. | |
| From: Dale Jacquette (Ontology [2002], Pref) | |
| A reaction: Worded with exquisite care! He does not say that ontology is reducible to semantics (which is a silly idea). We could still be committed, as in a ghost story, to existence of some 'nameless thing'. Things utterly beyond our ken might exist. |
| 7683 | Logic is based either on separate objects and properties, or objects as combinations of properties [Jacquette] |
| Full Idea: Logic involves the possibilities of predicating properties of objects in a conceptual scheme wherein either objects and properties are included in altogether separate categories, or objects are reducible to combinations of properties. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: In the first view, he says that objects are just 'logical pegs' for properties. Objects can't be individuated without properties. But combinations of properties would seem to need essences, or else they are too unstable to count as objects. |
| 7684 | Reduce states-of-affairs to object-property combinations, and possible worlds to states-of-affairs [Jacquette] |
| Full Idea: We can reduce references to states-of-affairs to object-property combinations, and we can reduce logically possible worlds to logically possible states-of-affairs combinations. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: If we further reduce object-property combinations to mere combinations of properties (Idea 7683), then we have reduced our ontology to nothing but properties. Wow. We had better be very clear, then, about what a property is. I'm not. |
| 7703 | If classes can't be eliminated, and they are property combinations, then properties (universals) can't be either [Jacquette] |
| Full Idea: If classes alone cannot be eliminated from ontology on Quine's terms, and if classes are defined as property combinations, then neither are all properties, universals in the tradition sense, entirely eliminable. | |
| From: Dale Jacquette (Ontology [2002], Ch. 9) | |
| A reaction: If classes were totally conventional (and there was no such things as a 'natural' class) then you might admit something to a class without knowing its properties (as 'the thing in the box'). |
| 15034 | Are genera and species real or conceptual? bodies or incorporeal? in sensibles or separate from them? [Porphyry] |
| Full Idea: I shall beg off talking of a) whether genera and species are real or situated in bare thoughts alone, b) whether as real they are bodies or incorporeals, and c) whether they are separated or in sensibles and have their reality in connection with them. | |
| From: Porphyry (Isagoge ('Introduction') [c.295], (2)) | |
| A reaction: This passage, picking up on Aristotle, seems to be the original source that grew into the medievel debate about universals. It seems to rather neatly lay out the agenda for the universals debate which is still with us. |
| 7685 | An object is a predication subject, distinguished by a distinctive combination of properties [Jacquette] |
| Full Idea: To be an object is to be a predication subject, and to be this as opposed to that particular object, whether existent or not, is to have a distinctive combination of properties. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: The last part depends on Leibniz's Law. The difficulty is that two objects may only be distinguishable by being in different places, and location doesn't look like a property. Cf. Idea 5055. |
| 7699 | Numbers, sets and propositions are abstract particulars; properties, qualities and relations are universals [Jacquette] |
| Full Idea: Roughly, numbers, sets and propositions are assumed to be abstract particulars, while properties, including qualities and relations, are usually thought to be universals. | |
| From: Dale Jacquette (Ontology [2002], Ch. 9) | |
| A reaction: There is an interesting nominalist project of reducing all of these to particulars. Numbers to patterns, sets to their members, propositions to sentences, properties to causal powers, relations to, er, something else. |
| 1350 | Continuity is needed for existence, otherwise we would say a thing existed after it ceased to exist [Reid] |
| Full Idea: Identity supposes an uninterrupted continuance of existence….Otherwise we must suppose a being to exist after it has ceased to exist, and to have existed before it was produced, which are manifest contradictions. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: I take the point to be that if something is supposed to survive a gap in its existence, that must imply that it somehow exists during the gap. If a light flashes on and off, is it really a new entity each time? |
| 21322 | We treat slowly changing things as identical for the sake of economy in language [Reid] |
| Full Idea: All bodies, as they consist of innumerable parts, are subject to continual changes of their substance. When such changes are gradual, because language could not afford a different name for each state, it retains the same name and is considered the same. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: This is hard to deny. We could hardly rename a child each morning. Simlarly, we can't have a unique name for each leaf on a tree. Economy of language explains a huge amount in philosophy. |
| 21320 | Identity is familiar to common sense, but very hard to define [Reid] |
| Full Idea: Every man of common sense has a clear and distinct notion of identity. If you ask for a definition of identity, I confess I can give none. It is too simple a notion. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: 'Identical' seems to be a two-place predicate, but the only strict way two things can be identical is if there is actually just one thing. In which case just drop the word 'identity' (instead of defining it), and say there is just one thing here. |
| 1367 | Identity can only be affirmed of things which have a continued existence [Reid] |
| Full Idea: Identity can only be affirmed of things which have a continued existence. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 6) | |
| A reaction: This doesn't mean that Reid thinks there is nothing more to the identity than their similitude. But he, like Hume, denies that there is personal identity at any given instant. Reid is better at criticism than at formulating his own theory. |
| 7691 | The actual world is a consistent combination of states, made of consistent property combinations [Jacquette] |
| Full Idea: The actual world is a maximally consistent state-of-affairs combination involving all and only the existent objects, which in turn exist because they are maximally consistent property combinations. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: [This extends Idea 7688]. This seems to invite the standard objections to the coherence theory of truth, such as Ideas 5422 and 4745. Is 'maximal consistency' merely a test for actuality, rather than an account of what actuality is? |
| 7688 | The actual world is a maximally consistent combination of actual states of affairs [Jacquette] |
| Full Idea: The actual world can be defined as a maximally consistent combination of actual states of affairs, or maximally consistent states-of-affairs combination. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: A key part of Jacquette's program of deriving ontological results from the foundations of logic. Is the counterfactual situation of my pen being three centimetres to the left of its current position a "less consistent" situation than the actual one? |
| 7695 | Do proposition-structures not associated with the actual world deserve to be called worlds? [Jacquette] |
| Full Idea: Many modal logicians in their philosophical moments have raised doubts about whether structures of propositions not associated with the actual world deserved to be called worlds at all. | |
| From: Dale Jacquette (Ontology [2002], Ch. 2) | |
| A reaction: A good question. Consistency is obviously required, but we also need a lot of propositions before we would consider it a 'world'. Very remote but consistent worlds quickly become unimaginable. Does that matter? |
| 7694 | We must experience the 'actual' world, which is defined by maximally consistent propositions [Jacquette] |
| Full Idea: Conventional modal semantics, in which all logically possible worlds are defined in terms of maximally consistent proposition sets, has no choice except to allow that the actual world is the world we experience in sensation, or that we inhabit. | |
| From: Dale Jacquette (Ontology [2002], Ch. 9) | |
| A reaction: Jacquette dislikes this because he is seeking an account of ontology that doesn't, as so often, merely reduce to epistemology (e.g. Berkeley). See Idea 7691 for his preferred account. |
| 23644 | Without memory we could have no concept of duration [Reid] |
| Full Idea: It is impossible to show how we could acquire a notion of duration if we had no memory. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], 1) | |
| A reaction: We would probably not have a notion of duration if we possessed a memory, but nothing ever changed. Maybe in Shoemaker's frozen worlds they retain memories, but nothing happens? |
| 23643 | We all trust our distinct memories (but not our distinct imaginings) [Reid] |
| Full Idea: Every man feels he must believe what he distinctly remembers, though he can give no other reason for his belief, but that he remembers the thing distinctly; whereas, when he merely distinctly imagines a thing, he has no belief in it upon that account. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], 1) | |
| A reaction: The word 'distinct' is doing some heavy work here. I fear that believing the memory is the only criterion we have for calling it distinct. As a boy I was persuaded to change my testimony about a car accident, and I realised I was not distinct about it. |
| 1356 | A person is a unity, and doesn't come in degrees [Reid] |
| Full Idea: The identity of a person is a perfect identity: wherever it is real, it admits of no degrees; and it is impossible that a person should be in part the same, and in part different; because a person is a 'monad', and is not divisible into parts. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: I don't accept this, because I don't accept the metaphysics needed to underpin it. To watch a person with Alzheimer's disease fade out of existence before they die seems sufficient counter-evidence. I believe in personal identity, but it isn't 'perfect'. |
| 7706 | If qualia supervene on intentional states, then intentional states are explanatorily fundamental [Jacquette] |
| Full Idea: If qualia supervene on intentional states, then intentionality is also more explanatorily fundamental than qualia. | |
| From: Dale Jacquette (Ontology [2002], Ch.10) | |
| A reaction: See Idea 7272 for opposite view. Maybe intentional states are large mental objects of which we are introspectively aware, but which are actually composed of innumerable fine-grained qualia. Intentional states would only explain qualia if they caused them. |
| 1359 | Personal identity is the basis of all rights, obligations and responsibility [Reid] |
| Full Idea: Identity, when applied to persons, has no ambiguity, and admits of no degrees. It is the foundation of all rights and obligations, and of all accountableness. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: This seems to me to be one of the key mistakes in all of philosophy - thinking that items must always be all-or-nothing. If a person deteriorates through Alzheimer's, there seem to be obvious degrees of personhood. Responsibility comes in degrees, too. |
| 21319 | I can hardly care about rational consequence if it wasn't me conceiving the antecedent [Reid] |
| Full Idea: The conviction of personal identity is indispensably necessary to all exercise of reason. Reasoning is made up of successive parts. Without the conviction that the antecedent have been seen by me, I could have no reason to proceed to the consequent. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: Society needs philosophers precisely to point such things out. It isn't conclusive, but populist waffle about the self not existing undermines the very concept of a 'train of thought', which everybody is signed up to. Trains of thought can take years. |
| 21323 | The identity of a thief is only known by similarity, but memory gives certainty in our own case [Reid] |
| Full Idea: A man challenges a thief in possession of his horse only on similarity. The testimony of witnesses to the identity of a person is commonly grounded on no other evidence. ...Evidence of our own identity is grounded in memory, and gives undoubted certainty. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: With other people the best we can hope for is type-identity, hoping that each individual being is a unique type, but with otherselves we are always confident of establishing token identity. Could I have been someone different yesterday, without realising? |
| 21321 | Memory reveals my past identity - but so does testimony of other witnesses [Reid] |
| Full Idea: Although memory gives the most irresistible evidence of my being the identical person that did such a thing, I may have other good evidence of things which befell me. I know who bare me and suckled me, but I do not remember those events. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: A splendidly accurate and simple observation. Reid's criticisms of Locke are greatly superior to those of Butler. We now have vast collections of photographs showing our past identities. |
| 21324 | If consciousness is transferable 20 persons can be 1; forgetting implies 1 can be 20 [Reid] |
| Full Idea: If the same consciousness can be transferred from one intelligent being to another, then two or twenty beings may be the same person. If he may lose the consciousness of actions done by him, one intelligent being may be two or twenty different persons. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 6) | |
| A reaction: Reid says Locke was aware of these two implications of his theory of personal identity (based on consciousness). The first example is me replicated like software. The second is if I forget that I turned the light off, then who did turn the light off? |
| 21325 | Boy same as young man, young man same as old man, old man not boy, if forgotten! [Reid] |
| Full Idea: Suppose a brave officer, flogged as a boy for robbing an orchard, to have captured a standard in his first campaign, and become a general in advanced life. [If the general forgets the flogging] he is and at the same time is not the same as the boy. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 6) | |
| A reaction: The point is that strict identity has to be transitive, and if the general forgets his boyhood that breaks the transitivity. If identity is less strict there is no problem. The general may only have memories related to some part of his boyhood. |
| 21327 | If a stolen horse is identified by similitude, its identity is not therefore merely similitude [Reid] |
| Full Idea: When a stolen horse is claimed, the only evidence that this is the same horse is similitude. But would it not be ridiculous from this to infer that the identity of a horse consists in similitude only? | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 6) | |
| A reaction: Actually that is exactly Hume's view of the matter (Idea 21292). For a strict empiricist there is nothing else be close resemblance over time. I prefer Reid's account to Hume's. - but then I am not a 'strict' empiricist. |
| 1366 | If consciousness is personal identity, it is continually changing [Reid] |
| Full Idea: Is it not strange that the identity of a person should consist in a thing (consciousness) which is continually changing? | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 6) | |
| A reaction: This is the panicky slippery slope view of Locke, that sees his doctrine as the first step to the destruction of religion. The fact is, though, that parts of my consciousness changes continually, but other parts stay the same for years on end. |
| 1352 | Thoughts change continually, but the self doesn't [Reid] |
| Full Idea: My thoughts, and actions, and feelings, change every moment: they have no continued, but a successive, existence: but that self, or I, to which they belong, is permanent. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: The word 'permanent' may be excessive, but one could hardly say there is nothing more to personal identity than the contents of consciousnes, given how much and how quickly those continually fluctuate. |
| 7704 | Reduction of intentionality involving nonexistent objects is impossible, as reduction must be to what is actual [Jacquette] |
| Full Idea: If intentionality sometimes involves a relation to nonexistent objects, like my dreamed-of visit to a Greek island, then such thoughts cannot be explained physically or causally, because only actual physical entities and events can be mentioned. | |
| From: Dale Jacquette (Ontology [2002], Ch.10) | |
| A reaction: Unimpressive. Thoughts of a Greek island will obviously reduce to memories of islands and Greece and travel brochures. Memory clearly retains past events in the present, and hence past events can be part of the material used in reductive accounts. |
| 7702 | The extreme views on propositions are Frege's Platonism and Quine's extreme nominalism [Jacquette] |
| Full Idea: The extreme ontological alternatives with respect to the metaphysics of propositions are a Fregean Platonism (his "gedanken", 'thoughts'), and a radical nominalism or inscriptionalism, as in Quine, where they are just marks related to stimuli. | |
| From: Dale Jacquette (Ontology [2002], Ch. 9) | |
| A reaction: Personally I would want something between the two - that propositions are brain events of a highly abstract kind. I say that introspection reveals pre-linguistic thoughts, which are propositions. A proposition is an intentional state. |